This invention relates to an internal combustion engine, and more particularly to the air intake system of an internal combustion engine.
In the power head of an outboard marine propulsion system, it is common to employ a two-cycle engine having its crankshaft oriented vertically to provide rotary output power to a vertically oriented drive shaft, with the engine cylinders being oriented horizontally. In a fuel injected engine, an air manifold is mounted to the engine for providing intake combustion air to the cylinders. The air manifold is typically mounted to the forward end of the engine nearest the boat, and includes one or more air inlet openings for receiving intake air for supply to the cylinders through the manifold. The forwardly disposed openings in the air manifold result in a relatively high level of noise in the boat during operation of the engine.
In addition, a commonly recognized problem in marine applications of internal combustion engines is that of keeping water away from the engine. As is known, numerous problems result from ingestion of water into the engine cylinders during operation of the engine.
The present invention has as its object to address the concerns noted above, namely ingestion of water into the engine cylinders and noise experienced by the boat operator and passengers during engine operation. It is a further object of the invention to provide a system for supplying intake air to the air manifold at as low a temperature as possible. Yet another object of the invention is to provide a system for supplying intake air to the air manifold which is simple in its construction and in its mounting to the engine.
In accordance with one aspect of the invention, a one-piece air intake and flywheel cover assembly is provided for the engine associated with the power head of an outboard marine propulsion system. The engine includes an engine block, an air manifold for supplying combustion air to the engine and having an opening for receiving intake air, and a flywheel connected to the end of a crankshaft rotatably mounted to the engine. The one-piece air intake and flywheel cover assembly comprises a flywheel cover portion defining an internal cavity for receiving the flywheel therein, and an air intake portion defining an air flow path including an air intake opening for providing intake air to the air flow path. The air flow path further comprises an air outlet in communication with the air manifold opening for supplying intake air thereto. The air manifold opening is formed in an upper surface of the air manifold, and the air intake portion of the assembly includes an air discharge passage providing a downwardly facing air outlet in communication with the upwardly facing opening in the air manifold. The internal cavity defined by the flywheel cover portion of the assembly includes a substantially circular side wall for covering the outer edge of the flywheel, and the air flow path is defined by an outer wall spaced outwardly from the flywheel cover side wall, with upper and lower walls extending between the outer wall and the flywheel cover side wall.
In accordance with another aspect of the invention, the air intake opening associated with the air flow path faces rearwardly, and the air manifold and its associated opening is located at the forward side of the engine closest to the boat. With this arrangement, engine noise exiting the air manifold through its intake intake opening is directed rearwardly away from the boat operator and passengers, thereby reducing engine noise in the boat. In addition, the length provided by the air flow path acts to attenuate the engine noise, further reducing noise levels in the boat.
In accordance with yet another aspect of the invention, the intake opening associated with the air flow path is located toward the upper end of the engine, which is typically enclosed by a cowl assembly providing one or more air vents for supplying air to the interior of the cowl assembly at the upper portion of the cowl assembly. Placement of the air intake opening in the upper portion of the cowl assembly provides intake air to the intake opening prior to the air passing over the engine, which otherwise would result in warming of the intake air. This prevents elevation of the air temperature, and accordingly avoids the losses in engine horsepower which would result from warmed intake air. Further, locating the air intake opening in the upper portion of the cowl assembly minimizes ingestion of water into the engine along with the intake air.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.